The present invention relates generally to a vapor compression system that uses the cold condensate from an evaporator to further subcool refrigerant exiting the condenser to increase system capacity and efficiency.
In a vapor compression system, refrigerant is compressed to a high pressure in a compressor. The refrigerant then flows through a condenser and rejects heat to a secondary fluid medium. The high pressure and relatively low enthalpy refrigerant is then expanded in an expansion device. The refrigerant then passes through an evaporator and accepts heat from another secondary fluid medium, such as air. The relatively high enthalpy and low pressure refrigerant then reenters the compressor, completing the cycle.
When refrigerant flows through the evaporator, moisture is removed from the air stream, and cold condensate forms on the surface of the evaporator coil. The cold condensate typically drips from the evaporator surface into a drain pan and is discharged from the system through a drain, for example.
It is desirable to further subcool the refrigerant exiting the condenser before expansion to increase system capacity and efficiency. In a prior art system, the cold condensate is collected and randomly sprayed directly on the surface of the condenser coil to assist heat rejection from the refrigerant in the condenser and reduce the discharge pressure of the refrigerant.
A drawback of this prior art system is that it is not effective, particularly in high efficiency vapor compression systems having large condenser coils, since the heat rejected in the condenser is still limited by the outdoor air temperature. As the size of the condenser coil increases, the amount of heat rejected in the condenser coil does not increase proportionally. Therefore, the cold condensate has little cooling effect on the large condenser coils. Thus, the driving force for the heat rejection diminishes, establishing a limit for further refrigerant temperature reduction.
There is a need in the art for a vapor compression system including additional heat rejection in the condenser and to further subcool the liquid refrigerant exiting the condenser to increase system capacity and efficiency.